Spark plug



1 the plug in such manner that arise in tem- Patented Sept. 25, 1923.

"UNITED STATES PATENT OFFICE.

' EDWARD 1. CURRAN, or DETROIT, MICHIGAN.

SPARK PLUG.

' Application filed October 8, 1921. Serial No. 506,269.

relatively low pressuresand the heavy duty I type which are constructed muchheavier and moresubstantial than the first type and are adapted for use in. marine engines, aeroplane engines and other engines where the compression is high and the pressure of the explosion is great. It is practically impossible to employ a low duty plug in a heavy duty engine for the reason that the plug, after a relatively short time, is invariably blown out or broken and rendered inoperative.

The main object of the invention is to provide a plug adapted for use for bothheavy and relatively light duty. engines, so constructed that it is not bulky or unwieldly, but is, on the contrary, of relatively small size and proportions, but of maximum strength to withstand the force of compression or power of explosion in the associated cyliner. I

-This object isattained through. the employment of novel plug. structure and the efcient proportioning of the parts, so as to withstand maximum pressures without necessitating the making of these parts large and bulky.

Another object of the invention is to so construct the plug that priming fiuid or' a decarbonizing fluid may be readily introduced into the associated cylinder through the plug in a novel, expeditious and highly efficient manner and to permit also of the blowing out'of oil orcarbon deposits from. the plug and associated cylinder through said plug. These features are accomplished through the employment of novel valve structureand the plug is so constituted that in the event a priming fluid is introduced, no surplus priming will be entrained in perature of the lug will render the entrained or enclose d surplus. fluid dangerous.

Other objects and advantages of the plug of this invention will be apparent from the hereinafter detailed description; from the drawing and from the appended claims.

While the plug may vary in form withoutdeparting from the present invention, it comprises, in one of its practical embodiments, a one-piece or integral shell, provided with a threaded nipple or shank adapted to. a be received into thetapped hole of the engine and all of the plug parts are at least partially housed within this shell. The central electrode is carried by an insulating member, preferably of porcelain and this insulating member is seated within the shell on a valve seat member provided with an upstanding tubular portion adapted to embrace that portion of the porcelain with which priming fluid or decarbonizing fluid would be apt to come into contact.

By this construction, the porcelain is protected against cracking, due to unequal expansion, particularly when relatively cold water is introduced into the plug while the plug is hot.

The novel form of tubular cylindrical valve cooperates with the valve seat and its interior constitutes a funnel shaped cup into which the priming or decarbonizing fluid may be readily poured, thereby adapting this operation to be easily and expeditiously carried out.

The valve seat member, as well as the valve itself collectively cooperate with the shell to hold the porcelain in place, so that it cannot be blown out when subjected to high pressures. The grounded electrode of the plug is preferably formed integral with the shell, while the central electrode of the plug is preferably swedged at its lower end to provide a cooperating plug point. The points of the plug may vary in shape, but, in practice, opposed knife edges are found to give very satisfactory and highly efficientresults.

Features of the invention, other than those specified, will be apparent from the hereinafter detailed description and claims, when read in conjunction with the accompanying drawings. I

The accompanying drawings illustrate one practical embodiment of the invention, but the construction therein shown,'is to be understood as illustrative, only, and not as defining the limits of the invention. I

Figure 1' shows a plug embodying the C-Il present invention partly in elevation and partly in central section.

Figure 2 shows the plug elements dismantled; and,

Figure 3 is a section on the line of Figure 1. 7

Referring to the drawings, 1 designates the shell of the plug and the shell is made somewhat longer than usual and is provided at its lower end with a ti rcaded shank 2 adapted to be screwed into the tapped hole or" a. motor cylinder head for the purpose of mounting the plug on the motor in the usual manner. The exte'ior of the shell is provided with a po ygonal portion 5 to permit of the application of a wrench thereto, so that the stem 2 thereby may be screwed tightly into the motor or moved therefrom.

The shell is provided interiorly at a point substantially midway between its top ant bottom with a shoulder 3 and above this shoulder the shell is interiorly threaded at at. That portion of: the shell below the shoulder 3 constitutes the plug chamber; which is divided into upper and lower parts 6 and 7, and the lower part of the shell is preferably so constructed that the ch mber 7 will taper upwardly through the torma tion of the wall of the threaded shank '2 with a downward taper.

The central metallic electrode 8 o plug extends entirely through the shell and beyond the upper end thereof l i and is enclosed for the greater portion of its length within an insulating member 9 preferably of porcelain. In practice, the porcelain is molded about the electrode 8 and thereafter baked so that the electrode is firmly embedded in the porcelain and becomes substantially homogenous therewith. thereby precluding the electrode from working loose within the porcelain and producing leakage through which compression might be lost.

The lower portion 10 of the insulating element 9 is preferably of substantially spherical contour and this portion 10 is sue mounted by an enlarged cylindrical portion 11, which is in turn, surmounted by a smaller cylindrical portion 12. The cylindrical portion 11 is of such size that it may be readily received into the upper portion of the shell 1 and come to a seat on a gasket 13 resting upon the shoulder It is held in this position by a valve seat memliier 11-. This valve seat member llis in the form of a ring, the outer circumference of which is threaded to engage with the threads of the shell and from the inner circumference of which extends an upstanding tubular sleeve 15. After the insulating member has been introduced into the shell and comes to a seat on the gasket 13, the valve seat member 14: is adapted to be screwed down into the top of the shell and comes to a seaton top of the enlarged cylindrical portion 1.1 of the insulating element. A gasket 16 is preferably interposed between these parts to pre elude leakage of compression.

The upper face of the valve seat member 14; is provided with an annular groove or channel 17, preferably V-shaped in section and this channel forms a valve seat. Vith this valve seat 17 cooperates a tubular valve 18, the lower portion of which is exteriorly threaded to engage with the threads =l of the shell and the upper portion 19 of which is polygonal to permit of the application of a rench to the valve in order that it may be screwed down tightly upon the seat 17. The lower edge or" the valve wall is bevelled both interiorly and exteriorly so that the lower edge of: such wall is substantially wedge shaped thereb enabling it to readily cooperate with the V-shaped seat.

It will be noted, however, that the taper of the valve is preferably less than the taper of the seat and this is the structure preferred, so that when the valve is screwed down tightly it will engage with the seat in two line contacts which assure a tight liquid seal and also preclude the leakage of compression.

The interior of the valve 18 is substantially funnel shape and this configuration permits of: the ready introduction of a priming or decarbonizing fluid into the plug. The fluid thus introduced into the interior of the valve 18 is adapted to find entrance into the associated cylinder by unscre 'ing the valve 18 to lift it from its'seat. The liquid is thus adapted to flow into the scat channel 17 downwardly from the base of which, at suitable intervals, circumferentially of the plug,- extend passages 20. These passages discharge the fluid into an annular channel 21 formed on the under side of the valve seat member 1 1. The liquid thus entering the channel 21 is adapted to flow through passages 22, which are formed in the enlarged cylindrical portion 11 and which serve to lead the liquid into the upper plug chamber 6, whence it flows through the lower plug chamber 7 into the associated cylinder.

In practice, the parts are preferably so assembled that the passages 22 are equal in number to the passages 20 and are placed in alinement with said passages, so that there will be a substantially straight-through flow of fluid from within the valve to within the plug chamben This is of particular importance when it is desired to blow off carbon deposits from the interior of the associated cylinder or oil or carbon deposits from the interior of the plug or associated cylinder. To accomplish this, it is only necessary to unscrew the valvelS for the purpose of unseating the same and thereafter to run the engine, while the valve is left open.

During the operation of blowing out foreign deposits in the manner described, the

funnel shaped valve interior is found to be of considerable importance since its, formation is such that there will be no back pressure and no possibilit of depositing the blown oil products on t e interior of the valve. They will be blown free from the plug, leaving all parts of the plug clean.

I have hereinbefore referred to the upstanding tubular sleeve 15, which is formed integral with the valve seat member 14 and embraces the porcelain 9 to a point'above the top of the valve member 18. I find that in practice this sleeve is of considerable practical importance since it serves-to fully and efiiciently breakage; his is particularly true when relatively cold water is introduced into the, valvewhen the plug is hot, in which event,

if the water'wer'e to come into direct contact with the heated porcelain within the confines of the valve, the sudden cooling of the porcelain would be [very apt to cause a breaking or cracking of-the'same.""The sleeve 15,

has the further function of however,

mechanically protecting. the porcelain against breakage when, subjectedto sharp scouring action of the gases entering the plug during its normal operation, the flow of which gases is caused by the explosion and compression of the motive fuel. The gases appear to flow into and out of the plug chamber from the associated cylinder and exert a scouring action on the interior of the shell 1 andalso onthe lower ball shaped end 10 of the porcelain, and the depending central electrode and serves to keep these parts free from oil or carbon deposits.

The sparking points of the plug of this invention may be constructed or formed in different ways, but a very practical construc tion is shown in the drawings. As shown, the grounded electrode 23 may be cast integral the shell 1 and is preferably in the 0 of an inwardly projecting spur,

the inner edge of which may be sharpened to a knife edge. The central electrode 8 may be conveniently swedged at its lower end to provide one or more radially projecting sparking edges or points 24,- the edges of which may be also sharpened to a knife edge.

In Fi central e ectrode is shown as provided with two sparking points orfedges, only one of which is used at any one time, but in case one burns of, the electrode, together with rotect the porcelain against ures 2 and 3 of the drawings, the

the porcelain9 may be rotated, so as to present the other sparking point for cooperation with the grounded point 23. If desired,

however, any, number of sparkingpoints may be provided on'the central electrode and k a corresponding number of integral spurs 23' be formed'on the shell. t will ap ti'cally all of the operating parts of the plug and furthermore that the lower end of the shell, is screwed, into the "engine cylinder,

while the porcelainis locked against blowair from the foregoing specifia cation that t 1e shell has housed therein prac-- ing out under high'pressures not only by the valve seat member '14. but also by the valve 18. In other words", both the parts 14 and 18 are threaded directly into the shell and hold orsback up the; porcelain, so it cannot possibly be blown out when the plug is employed on heavy duty engines employing high compression and high explosive pressures. By making the shell l relativelylo ng and v tightening the partstogether inithe manner described, 1 am enabled to obtain unusually strong and efficient pressure resisting plug without rendering the same unduly fheav'y. In fact, the plug isbut littleheavier than the ordinary light duty plug now in common use, yet it is capable of with standing the maximum pressures developed in heavy duty engines. I I

In the foregoing detailed description and in the accompanying drawings, the invention has been set forth in its preferred, practical form, but I am aware that details of construction may be varied, for example, by the substitution of equivalents without departing from the spiritor substance of this invention, which is tobe understood as broadly novel as is commensurate with the appended claims. 1

Having thus fully described the invcntion, what I-claim as new and desire to secure by Letters Patent is:

1. A spark plug embodying a shell, one end of which is 'extcriorly. threaded to screw into the tapped hole. of a cylinder, the other endiof which shell is intcriorly threaded, a

shoulder formed interiorly of said shell and intermediate the ends'thereof, an insulating member provided intermediate its ends with an enlarged ortion adapted to seat on the interior shoul er of the shell, a valve seat member screwed intothe interiorly threaded por- 'tion of the shell, and bearing against the enlarged portion of the insulating member to force it to a seaton the shoulder of the shell,

. passages leading through the valveseat memr her, and through the enlarged portion of the insulating member, through which liq uid may pass into the associated cylinder, and a valve member threaded to engage with the interior threads of the shell, and formed to simultaneously'seal or unseal all of the I Cit larged portion of the inside.

diate its ends with an, enlarged port-ion adapted to seat on the interior shoulder of the she... a valv seat member ilu'eaded portion =gainst the en.-

serewed into the interiorlv of the shell and bearm inp: member to force it to a seat; on the ioulder of the shell. passages leaning through the valve seat member and through the enlarged portion of the insnlatin member, through which liquid may pass into the associated evlinder. and a cylindrical valve member threaded to engage with the interior threads of the shell and. formed to simultaneously seal or unseal all of the passages when said valve is rotated into and out of engagement with the valve seat member. the interior of the cylindrical valve forming a basin adapted to contain the liquid to be passed through the plug into the (-ylinder.

A siark olug einhodvin a shell. .one.

l n E 1 end of which is exteriorlv threiuled to screw into an engine cylinder, and the other end of which interiorlv threaded. an insulating member rigidly mounted within the shell and extending above the top'thereof, a va ve seat member cooperating with the interior threads of the shell and screwed thereinto. said valve seat member being provided with an integral sleeve embraring that portion of the insulating member within the shell and above the seat member. and a tulni..:n' 'alvo also associated.

with the interior threads of the sleeve and eooperating with the valve seat member. the interior of said tubular valve forming a basin adapted to contain liquid to be introduced into the associated engine c vlin-' In testimony whereof I'have signed the foregoing specification.

EDWARD T. oUn mix. 

